Print production processes implement both sheetfed and web offset lithography devices such as printing presses that print, respectively, onto individual sheets and large rolls of paper. In either case, these print production processes typically employ one or more post-print finishing devices that perform additional finishing operations on printed material after printing has been completed. A finishing operation generally includes any post-printing process, such as slitting, trimming, die-cutting, folding, coating, embossing, and binding. Finishing operations can be performed by one or more finishing devices that are in-line or near-line with the printing device.
With in-line printing processes, finishing devices are connected directly to a single printing device so that printed material passes directly from the printer to the one or more in-line finishing devices without being removed from the process and taken to other devices. With near-line printing processes, finishing devices are not connected directly to a particular printing device, so printed material (e.g., stacks of printed sheet paper) needs to be demounted from the printing device and remounted on the one or more near-line finishing devices. While the need to transfer printed material to near-line finishing devices seems disadvantageous, it has the advantage of allowing near-line finishing devices to process printed material from more than one printing device. In general, advantages and disadvantages between the use of in-line or near-line finishing devices depend on factors such as printing speeds, finishing device processing speeds, printer down-time, and so on.
One challenge that persists with regard to sheetfed print production processes is achieving an accurate alignment of the sheet paper between the printing device and the finishing device. Paper sheets are cut to standard sizes, such as “A”, “B”, and “C” series paper sizes, and various standards specify tolerances for the different sized sheets. For example, the tolerance for a “B2” sheet size is ±2-3 mm under the international paper size standard, ISO. When changing between different printing modes (e.g., simplex and duplex), the printing device and finishing device can align the sheet of paper to opposite edges. Is such cases, the paper tolerance can create alignment inaccuracies with in-line finishing processes.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.